Control apparatus



Oct. 1, 1957 J. LlEBE RMANN CONTROL APPARATUS 2 Sheets-Sheet 1 Filed Aug. 6, 1954 FIG. I

FIG. 7

I INVENTOR FIG. 8 JOHN LIEBERMANN BY 2 r6 I ATTORNEY Oct. 1, 1957 J. LIEBERMANN 2,808,478

CONTROL APPARATUS Filed Aug. 6, 1954 2 Sheets-Sheet 2 JOHN LIEBERMANN BY @e.

ATTORNEY.

2,808,478 Patented Oct. 1, 1957 CONTROL APPARATUS John Liebermann, Columbus, Ohio, assignor to Ranco Incorporated, Columbus, Ohio, a corporation of Ohio Application August 6, 1954, Serial No. 448,326

2 Claims. (Cl. 20030) The present invention relates to control apparatus, and more particularly to electric switch mechanism for periodically initiating defrost cycles in refrigerating systems and terminating the cycles in response to temperature conditions or after a predetermined lapse of time as a safety measure to prevent undesirable or dangerous rises in temperatures in the system.

The present invention is an improvement of the type of switch mechanisms comprising two spring blade contact members arranged to follow a rotating cam periphery and make electrical contact with one another, the cam being formed to move the blades together in one direction to a position in which one blade is held by a latch against following the other blade in the opposite direction, after which the last mentioned blade drops to a low part of the cam thereby snap separating the contact blades, after which the latch is operated to release the latched blade and cause re-engagement of the blades by snap movement.

It has been the practice to cause the latched blade to move its latching member to one side thereof by a wedging action of the latching surfaces as the blade is moved to its latched position, which action produces a load on :the cam driver and is also conducive to Wearing of the ;interlatching surfaces. An object of the present invena-tioin is to provide means by which the latch is temporarily z-IHOVBd to the blade releasing position until after the blade is in position for latching, after which the latch is moved .to its latching position so that wear on the critically dirnensioned latching surfaces is practically eliminated and appreciable loading of the cam driving mechanism is avoided.

Another object of the invention is the provision of an improved switching mechanism having a convenient ar rangement for factory adjustment of the latch mechanism to accurately time the release of the latched switch blade.

Other objects and advantages of the invention will be apparent from the following description of a preferred form of the invention, reference being made to the accompanying drawings wherein:

Fig. 1 is a perspective view of a defrost control for a refrigerating system, which control embodies the invention;

Fig. 2 isa side elevational view of the defroster control with a side cover plate removed and certain parts broken away;

Fig. 3 is a sectional view taken along line 33 of Fig. 2 but on a larger scale and turned ninety degrees;

Fig. 4 is a fragmentary view of the control similar to Fig. 3 but on a larger scale and showing the switch parts in diiferent positions;

Fig. 5 is a sectional view taken substantially along line 5-5 of Fig. 6;

Fig. 6 is a view similar to Fig. 4, but showing the switch parts in different positions;

Fig. 7 is a plan view of a cam; and

Fig. 8 is a graph representing relative actions of certain elements of the control in time, produced by cam surfaces.

Although the control apparatus may have many uses, it is here shown in the form of a defroster control for an electrically operated refrigerator. The defroster control, shown generally at C, comprises a housing 10 which is formed by a channel shape member having end portions turned at right angles to provide integral front and end walls 11, 12, 13. A channel shape rear wall 14 is attached to the open side of the first mentioned member, as by screws one of which is shown at 15. Side plates 16 are arranged to have edge portions inserted within the sides of certain of the channel members so that the plates are frictionally held in place to close the sides of the housing. A mounting bracket 17 is suitably attached to the outer side of the front wall 11 to provide a convenient means to attach the control to a part of a refrigerator. The details of the housing are not important to the invention and are not discussed.

A conventional timer motor M and gear train are attached to the inside of the front wall 11 and the train is arranged to drive a shaft 20, which projects from opposite sides of the gear train casing, at the rate of one revolution per day, although the rate of drive could be any desired. The drive between the gear train and shaft 20 includes a one way clutch 21 which permits the shaft to be rotated manually in one direction but which blocks rotation in the opposite direction. Such clutch mechanism is well known and it is not disclosed in detail here. The shaft 20 has a driver spur 22 toward the outer end by which a knob, not shown, can be drivingly connected with the shaft, the knob being accessible to the user of the refrigerator.

The inner end of the shaft 20 has a cam 25 thereon which is attached to the shaft for rotation therewith, and the cam is normally driven at the rate of one revolution per day. The cam 25 is preferably formed of insulating material, such as Bakelite, and has two cam faces 26, 27. The face 26 is generally cylindrical and is arranged to move a follower thereon toward and from the axis of shaft 20, and face 27 has rises arranged to move a cam follower in a direction generally parallel to the axis of the shaft as is explained fully hereinafter.

Three switch blades 30, 31, 32 have one end thereof attached in an insulator block 33 which is mounted in an opening through the rear wall and attached to the wall by screws 34. The blades 30, 31, 32 are spaced from one another and have individual terminals 35, 36, 37 connected thereto and the blades proper extend in generally parallel, spaced relation. The blade 30 rests against the cam surface 26 and is normally biased to engage the cam surface. Blades 31, 32 are likewise biased toward the cam, and blade 32 is maintained spaced from blade 30 by a link 38, which is formed of insulating material, such as phenolite, and extends freely through an opening in the central blade 31. The blades have contacts 40, 41, 42 attached thereto respectively and contacts 40 and 42 are arranged to engage contact 41, which is a double contact as shown.

The cam surface 26 has a rise 45 thereon which is adapted to move the contact blades to the right or outwardly from the cam axis, the contact 41 of blade 31 being engaged with contact 40 during this movement, and blade 32 being maintained spaced from electrical engagement with blade 31 by the spacer link 38 as shown in Fig. 4. The blade 31 is arranged to be latched in its outer position and restrained from following the blade 30 by a latch, described more fully hereinafter, after which blade 30 is snapped from blade 31 by dropping from the high to the low point of a step 46 formed in the cam surface 26. This movement of blade 30 causes blade 32 to snap move toward blade 31 to engage contact 42 with contact 41. Terminals 35, 36 may be connected in the circuit of the refrigerator compressor motor, for example,

and terminal 37 connected in one side of a circuit for an electric heater for applying heat to the evaporator of the refrigerator, the terminal 36 being connected to a common line of the power source. Thus, the compressor motor is de-energized when the heater circuit is energized and vice versa. Terminal 36 includes a connection with one lead of the motor M and a terminal 48 is provided to connect the other lead of the motor to a suitable power source common with terminal 36.

The latch for the blade 31 comprises a U-shape stamping 50 pivoted on a pin 51 supported in openings in opposite sides of the end wall 12. An insulating plate 52 is riveted to the yoke of the member 50 and projects opposite the end of the blade 31 and has a metallic latch plate 53'attached thereto which provides a lip 54 against which the end of blade 31 abuts and which thereby prevents the blade from following blade 30 until the member 56 is tilted counterclockwise about its pivot to cause the lip to raise from engagement with the blade. The member 50 includes an arm 55 which entends over the cam surface 27 and has a bump 56 which rides on the last mentioned cam surface. The member 50 is urged clockwise about its pivot by a tension spring 57 having one end attached to one leg thereof and the other end attached toan arm 60 of a thermostatically operated lever 61 described more fully hereinafter. The spring 57 normally retains the outer end of arm 55 in a downward position, as viewed in the drawings so that the arm is engaged by two fairly abrupt rises 62, 63 of cam surface 27 which move the arm to a position in which the latch lip 54 is out of alignment with the blade 31, that is to say, the latch is moved to its release position. The rise 62 is arranged relative to the rise 45 so that the arm 55 is moved to cause the latch lip 54 to rise out of alignment with blade 31 just prior to and during the movement of the blades by the rise 45. Prior to the step 46 releasing blade 30 the rise 62 drops off to permit the latch lip to be lowered to latch the blade 31 as described. This timing of operation is illustrated in Fig. 8 wherein lines 26, 27 represent the action of the switch blades by the cam 26 and the latch by the cam 27, respectively. It will be seen that rise 62 renders the latch inoperative at the time indicated by vertical line a and cam rise 4-5 moves the switch blades to the latching position at the time represented by the vertical line b. The rise 62 releases the latch at the time represented by line well in advance of the release of the blades by the step 46 at the time represented by line d.

The, latch is adapted to be operated by a thermostatic device to release blade 31 in response to a predetermined temperature of the refrigerator cooling unit above the melting point of frost and comprises a wafer type expansible element 7@ attached to a plate 71 arranged to be secured inan opening in the end wall 12. The element 70 includes a tube 72 closed at one end and connected at the other end with the interior of the wafer 70. The element and tube contain a suitable volatile fiuid which changes in pressure according to temperature changes in a range including frost melting temperature. The movable wall of the element has a post 73 attached thereto, which post has an overhanging button formation on the outer end thereof under which a cross piece 74 of the member 61 extends. The lever 61 is pivoted on the pin 51 and is urgedcounterclockwise by a tension spring 75, shown in Figs. 2, 5, having one end attached to a plate 76 threaded on a screw 77 rotatably supported in the front wall 11, and the other end of which spring is connected to an arm 78 of the lever 61. It will be seen that the effect of spring '75 is to urge the cross piece 74 in a direction to expand the element 70, which expansion is resisted by atmospheric pressure on the element, the fluid pressure within the element being below atmospheric pressure. The fluid charge in the element 70 is such that at normal refrigerating temperatures the element is in a relatively collapsed state and lever 61 will have moved clockwise.

During a defrost cycle, the temperature of the cooling unit rises and the element 70 expands which permits lever 61 to be moved counterclockwise by the spring 75 which moves the arm 60 against a lateral foot 76 of member 54), moving the latter counterclockwise and causing the latch to release blade 31.

In the event the element 70 should lose its charge, the force of spring 75 maintains the latch in the blade releasing position and the defrost cycle is never initiated, or if the charge is lost during defrosting, the defrost cycle is terminated.

The rise 63 on the cam surface 27 is located so that within a given period following the time blade 30 drops off of step 46, which time interval is represented as that between lines of and 2 Fig. 8, lever 55 is moved thereby to a position to release blade 31 in the event the latch has for any reason failed to be operated by the thermostatic device within the predetermined period mentioned.

Preferably, the latch operating arm 55 is formed of metal which can be bent to adjust the angular position of the latch member 52 and the arm so that during factory assembly of the apparatus the rise 63 of the cam face 27 can be made to cause arm 55 to actuate the latch 54 to release blade 31 at the desired predetermined time following the actuation of blade 30 by the cam step 46.

It will be seen that by my invention, the blade 31 is moved to its latched position by a minimum of effort on the part of the motor and without frictional engagement with the latch lip 54 with the blade 31 whereby accuracy of operation is maintained by the elimination of wear and bending or deformation of the parts. Thus, although the switch mechanism operates by critical and minute movements, the operation thereof can be maintained ac curate throughout long usage. Furthermore, it will be seen that the switch mechanism is convenient to assemble and is easily adjusted for proper operation.

While I have described but one form of the invention, it will be understood that other modifications, adaptations and uses thereof may be employed within the scope of the claims which follow.

I claim:

1. Control apparatus comprising first and second engageable contact members movable relative to one another to, make and break an electric circuit therethrough, means including a cam to move said first contact member in opposite directions alternately, both of said contact members being moved to one position together by said means, a latch movable transversely of the direction of movement of-said second contact member to thereby engage an edge portion thereof and retain said second member in said one position, and means including a cam synchronized with the first mentioned cam for moving and maintaining said latch out of range of movement of said second member during movement of said contact members to said one position and for moving said latch to its contact member latching position prior to movement of said first contact member from said one position whereby saidfirst contact member is moved from said second contact member.

2. Control apparatus comprising a rotatable cam including a first camming surface having a gradual rise and an abrupt step, a pair of spring biased contact members urged toward said cam surface, a first contact member engaging said surface and the second contact being engageable with the first contact memberwhereby both contacts while engaged are moved gradually by said cam against their bias to one limit of movement, a pivoted arm having a latch part swingable into and out of the path of movement of said second contact member to engage and prevent said second member following the first member when said first member is released by said step in said cam surface, a second cam surface on said cam, said arm having a part riding on said second cam surface and being moved thereby to swing said latch part out of the path of movement of said second contact member during gradual movement of said members to said limit and to swing said latch part into the path of said second member prior to the release of said first contact member by said step in said first cam surface, and means to move said arm to swing said latch part from the path of movement of said second member to release the latter for snap movement into engagement with said first member.

References Cited in the file of this patent UNITED STATES PATENTS Bartels et a1. July 21, 1942 Cowardin July 11, 1950 Morrison Jan. 29, 1952 Morrison Sept. 28, 1952 Coe Jan. 4, 1955 

